1. Field of the Invention
The present invention relates to recording apparatuses and methods, playback apparatuses and methods, and to recording media therefor. More particularly, the invention relates to a recording apparatus and method suitable for, for example, compressing audiovisual (AV) signals and recording them on information recording media, and to a recording medium therefor. The invention also pertains to a playback apparatus and method suitable for, for example, converting AV signals recorded on information recording media as packetized elementary stream packets into transport streams and outputting them, and to a recording medium therefor. The invention also relates to a recording apparatus and method and a playback apparatus and method suitable for, for example, recording and reading different types of data streams on and from information recording media, and to a recording medium therefor.
2. Description of the Related Art
As the DV format used for consumer video cassette recorders (VCRs), a system is provided for coding video signals by performing intra-frame compression and coding the corresponding audio signals without compressing them or coding the audio signals so that they can be instantaneously companded, and then for recording the encoded video signals and audio signals on magnetic tape.
Video signals and audio signals encoded in the DV format and recorded on recording media are suitable for editing the corresponding images and sound so that they can be spliced at a certain position.
However, because of a low compression rate of the DV format, a system having a high transfer rate and a medium having a large storage capacity are required, and also, the recording time becomes shorter if the capacity of an information recording medium is limited.
To overcome the above-described drawbacks, a system for compressing video signals and audio signals according to an Moving Picture Experts Group (MPEG) method and for recording them in the form of transport stream (hereinafter sometimes referred to as “TS”) has been proposed and is used.
According to the system using the MPEG method, video signals are encoded by compressing a long group of pictures (GOP) formed of a plurality of frames according to the inter-frame compression method, while audio signals are encoded by compressing a plurality of samples according to the frame compression method, thereby achieving a high compression rate. Accordingly, the provision of a recording system having a high transfer rate becomes unnecessary, space can be saved on the recording medium, and the recording time becomes longer compared to a DV-format system even if the capacity of the recording medium is limited.
However, in a system in which MPEG-compressed video signals and audio signals are recorded in the form of TS, the following problems are presented.
That is, as stated above, video signals are MPEG-compressed in units of long GOPs, the length of one frame of an image varies according to the type of image (Intra (I) picture, Predictive (P) picture, and Bidirectionally predictive (B) picture) or the design of the image. In other words, the video signals are not compressed at a constant rate. In contrast, audio signals are compressed at a fixed rate. Accordingly, even if the video signals and the corresponding audio signals are simultaneously encoded, the packets of the video signals and the corresponding packets of the audio signals may disadvantageously be separately disposed on a TS.
In this case, if images and sound are edited so that they are spliced at a certain position on a TS, there may be temporal displacement in the continuity between video frames and audio frames, or one of the video frames or the audio frames may be missing.
It is also necessary to add to a TS a TS header, a time stamp indicating the arrival time of video signals and audio signals at a decoder, and a program clock reference (PCR) packet for storing a PCR, which is the reference time for a decoding operation. Accordingly, the overhead becomes larger, and the recording rate is lowered.
In addition, it is difficult to perform so-called “jog playback”, such as pause, slow, and reverse playback, on video signals and audio signals. To enable the jog playback operation, it is necessary to convert TSs to elementary streams.
Moreover, an error may occur in a video signal or an audio signal in the form of a TS during a reading or playback operation, thereby adversely influencing the image quality or the sound quality.